Mobile communication systems continue to grow in popularity and have become an integral part of both personal and business communications. Various mobile devices now incorporate Personal Digital Assistant (PDA) features such as calendars, address books, task lists, calculators, memo and writing programs, media players, games, etc. These multi-function devices usually allow electronic mail (email) messages to be sent and received wirelessly, as well as access the internet via a cellular network and/or a wireless local area network (WLAN), for example.
As the functionality of cellular communications devices continues to increase, so too does demand for smaller devices that are easier and more convenient for users to carry. Nevertheless, the move towards multi-functional devices makes miniaturization more difficult as the requisite number of installed components increases. Indeed, the typical cellular communications may include several antennas, for example, a cellular antenna, a global positioning antenna, and a WiFi IEEE 802.11g antenna. These antennas may comprise external antennas and internal antennas.
As the internal space of the cellular communications device becomes more limited, it may be more difficult to achieve certain performance metrics. For example, some communications standards include out-of-band interference mitigation requirements. An approach to improving performance is to control the phase of a transmitted signal. In particular, there is a desire to control the phase shift of a transmitted signal at varying points in an antenna element.